Hardware Reference
In-Depth Information
can connect the network—and can have several features in common—only switches are
normally used today. The differences between them are significant and are covered in the
following sections.
All Ethernet switches have the following features:
• Multiple 8P8C (RJ-45) UTP connectors
• Diagnostic and activity lights
• A power supply
Ethernet switches are made in two forms: managed and unmanaged.
Managed
switches
canbedirectly configured, enabled ordisabled, ormonitored byanetworkoperator.They
arecommonlyusedoncorporatenetworks.Workgroupandhome-officenetworksuseless
expensive
unmanaged
switches, which simply connect computers on the network using
the systems connected to it to provide a management interface for its configurable fea-
tures.
Signal lights on the front of the switch indicate which connections are in use by com-
puters; some also indicate whether a full-duplex connection is in use. In addition, multis-
peed switches may indicate which connection speed is in use on each port. A switch must
have at least one 8P8C (RJ-45) UTP connector for each computer you want to connect to
it.
How Switches Work
UTPEthernetnetworkswereoriginallywiredusinghubs.Whenaspecificcomputersends
a packet of data to another specific computer through a hub, the hub doesn't know which
portthedestinationcomputerisconnectedto,soitbroadcaststhepackettoalloftheports
and computers connected to it, creating a large amount of unnecessary traffic because
ports and systems receive network data even if it is not intended for them.
Switches, as shown in
Figure 17.17
,
are similar to hubs in both form factor and function,
buttheyareverydifferentinactualoperation.Aswithhubs,theyconnectcomputersonan
Ethernet network to each other. However, instead of broadcasting data to all of the ports
and computers on the network as hubs do, switches use a feature called
address storing
,
which checks the destination for each data packet and sends it directly to the port/com-
puter for which it's intended. Thus, a switch can be compared to a telephone exchange,
making direct connections between the originator of a call and the receiver.
Figure 17.17
Front (top) and rear (bottom) of a typical five-port, 10/100 Ethernet switch.
